Packaging materials typically used for packaging foods, drinks, and the like have been required to have wide variety of functions, for example, not only functions, such as, strength, resistance to cracking, retort resistance, and heat resistance but also excellent transparency capable of examining contents in order to protect contents from various types of distribution, preservation, e.g., cold storage, treatments, e.g., heat sterilization, and the like. On the other hand, in the case where bag is hermetically sealed by heat seal, a cast polyolefin film having excellent thermal workability is indispensable. However, the cast polyolefin film do not have many functions as the packaging material. In particular, a high barrier property has been strongly required for the purpose of holding quality of the content and holding the amount of the content. Such barrier packaging material is usually used as a composite flexible film in which different types of polymer materials and inorganic materials are stacked.
When a barrier function is imparted to a multilayer film, it is difficult to impart the barrier function to the cast polyolefin films used for an inner layer (sealant side) by coating or vapor deposition. Consequently, in many cases, the barrier function is imparted to various films (polyester resins, e.g., polyethylene terephthalate (hereafter abbreviated to PET), polyamide resins, and stretched olefin resins) used for the outer layer side.
In the case where the barrier function is imparted to these outer layer side films, vinylidene chloride exhibiting high retort resistance and gas or water vapor barrier property has been frequently used, although there are problems that, for example, dioxin is generated during burning for disposal. Also, in the case where polyvinyl alcohol resins and ethylene-polyvinyl alcohol copolymers are used as barrier coating materials, an oxygen barrier property is high, although there is a problem that a water vapor barrier property is degraded significantly. Also, a film provided with a vapor deposition layer of metal oxide, e.g., silica or alumina as a gas or water vapor barrier layer is expensive and, in addition, has problems that the flexibility is poor and gas•water vapor barrier performance is varied because of cracks and pinholes.
As for sheets having a water vapor barrier property, for example, PTL 1 describes a sheet containing cyclic olefin in the resin composition and exhibiting excellent water vapor barrier property, impact resistance, rigidity, and heat resistance and a container formed from the sheet.
Also, PTL 2 describes a material which is a film or a sheet containing a vinylidene chloride based copolymer.
As for a material having a tricyclodecane skeleton, for example, PTL 3 describes an example of use of maleimide compound having a condensed alicyclic structure and it is mentioned that the water vapor barrier property can be imparted to the obtained sealing agent.
Also, PTL 4 mentions that polyurethane is developed as an adhesive for transparent inorganic vapor deposition film and an anchor coating agent, polyester polyol is use as a raw material for polyurethane, and tricyclodecane dimethanol is used as a glycol component.